Mechanical stoker



Jan. 23 1951 E. c. MILLER 2,538,944

MECHANICAL STOKER Filed Oct. 4, 1945 2 Sheets-Sheet l J 233 191 E. c.MILLER 205389944 MECHANICAL STOKER Filed Oct. 4, 1945 2 Sheets-Sheet 2Patented Jan. 23, 1951 UNITED? STATES PATENT OFFICE MECHANICAL STOKEREarle? C; Miller. Worcester 'Mass, assighor to Riley StokerGdrporationg. Worcester, Mass:,-. a corporation .of MassachusettsApplication October-4, 1945, Serial No; 620.243

7. Claims;- (Cl. 1598 128) This invention relates to' mechanicalstoliers. and more particularly to stokers ofthesc -called" spreadertype having" revolving blades to throw fuel particles into a furnace forcombustiontherein.

Spreader stokers usually comprise a horizontal rotor mounted in front ofan opening in a furriace wall and carrying a series of blades'to whichthe fuel is supplied by a' suitable feedingmechanism. The furnace isprovided with a grate which supports a bed of burning fuel, and theblades throw fue1 through the wall opening so that the veryfineparticles may burn in suspension while the coarser particles aredeposited on the fuel bed. Since the' widthof the grate usuallyconsiderably exceed the length of the rotor", the rotor must spread thefuel laterall'yin order to" obtain uniform fuel distribution over thegrate. This problem is complicated by the fact that grates of manydifferent widths are encountered in various installations;Priorstoke'rshave been lacking in the ability to'spread the fuel in auniform manner; and'particularly lackingin adapta bility' for use withvarying grate widths; The

rotors are necessarilyexposed toconsiderable heat radiating outwardlythrough the" wall" opening;

and this has? caused warpingof shafts and other It is accordingly oneobject of the invention to provide an improved construction fortherotoif of a spreader. stoker whereby a moreuniform dis-- tribution ofthefuel may be obtained.

It is a further objectofthe invention to provide a spreader stoker rotorhaving simple and de pendable means whereby the distribution of the.fuel may be altered to adapt the stoker to grates of varying'widths.

It is a further object of the invention to provide a spreader stokerinwhich the rotoris more 2 Fig. 2 is" a sectiontaken on theline 2- 2 or:

1 Fig. 3'- is a view similar to Fig. 2, but'showihgi therotor turned90-degrees ina forward dirc-.

tibn';

Fig. 4" is an enlarged section taken on the 4' !of Fig. 2';

Fig. 5 is a detail view of ahub' member; Fig. 6" is a perspective viewof" a hub member:- I and Fig; "7 is' a perspective View of a fuelimpeller 01' paddle.

The embodiment illustrated comprises an" up= right furnace wall Hihaving a laterally elong'a 'd' rectangular opening H therein; This openrig flares both vertically and horizontallytoward the rear orfurnaceside of the wall. The usualmetal front plate 1'2" is provided onthe" front or outer side of'the-wall', this plate having an opening Mwhich registers with the wall opening II. The furnace will be providedwith asuitable grate (hot shown) below the opening ll, and inac cordancewith the customary practice this-grate will be appreciably widerthan theopening. in thecase of wide furnaces, a plurality of wanopenings 'willbe provided;

Referringgnow to-Figs. I and 2;. it willbe seen that a semicylindric'al" trough or'rotor casing" f6 is" mounted on the front platet2 immediately below the opening W, this'troughbeirig clbsedat its endsby upright Walls ll. Withinthetrough' there is provided" arotorcomprising, a horizontal shaft I8" which" extends along" the axisof" the trough andparallelwith the front plate 2, this line 35; shaftbeing rotatably' supported in bearings?!) of any suitable type carried"by the end walls f1 of the trough. The shaft I3" is rotated by anysuitable means in an over rurining direction such that its upper"surface travels toward the 7 furnace, and on this shaft there aremounted. impellers or paddles 2! arranged" to throw" fuel rearwardlythrough the wall opening H. The front wallof the trough it extendsupwardly'ahd isprovided at its upper edge with a forwardly pl'ate- 24;This plate-extends rearwardly'over' the trough; there'ar' edge"- or theplate beihg located above the rotor; A ram' 25'" is slidably supportedon the plate 2 and arranged to be" reciprocated 50? forwardlyand'rearwardly bysuitable rockerarms 2 -3-1 fuel hopper- '28isinriounted' above therani- 253 Thishopper sup f-uel tathe rain; andthe latter pushesfuel at a clesi red rate rearward-1y over the; plate 2the fuel moppingfro-mthe 65? rear edge of-thisplat'e into'the path ofthe irh pellers 2|. The trough I6 is preferably constructed with aremovable section 39 in its lower front portion to permit ready accessto the rotor.

The rotor is constructed in a novel manner to provide great practicaladvantages. Thus the rotor shaft I8 is formed with a plain cylindricalouter surface, this shape being the simplest and least expensive tomanufacture and the least likely to be distorted by heat. Along theshaft there are mounted a series of hubs each of which comprises a pairof oppositely disposed hub members 32. Each of these members 32 has aflat or plane outer surface 33 and an inner surface formed with asemi-cylindrical groove 34 for engagement with the shaft, the surface 33being parallel with the groove axis. At one side of this groove there isprovided a plain hole 36, and at the other side there is provided athreaded hole 31. An additional threaded hole 38 is provided through thefiat surface 33 and intersecting the groove 34, this hole being offsetlaterally from the axis of the groove in a direction toward the plainhole 36. The two members 32 of each hub are clamped against the shaft LGby means of two screws 48 which extend through the plain holes 36 andinto the threaded holes 37, the arrangement being such that when amember 32 is on the top of the shaft the corresponding plain hole 36will be in front of the shaft. As shown in Figs. 2 and 3, the hubs arespaced rather closely together along the shaft, and adjacent hubs areturned 90 degrees with respect to one another. In the embodimentillustrated nine hubs are provided, but this number ma be varieddepending upon the width of the wall opening I I.

These hubs support pairs of opposed impellers 2|. As best shown in Figs.4 and '7, each impeller comprises a fiat blade 32 and a base 43 integralwith the blade, these portions being at approximately right angles toprovide a structure L- shaped in cross section. The base is providedwith a plain hole 45 for the reception of a single screw 46 whichextends into the threaded hole 38 and thus fastens the base against theflat surface 33 of the hub member 32, the blade 42 being in advance ofthe base 43 in the direction of rotation. The width of the blades 12,measured parallel with the axis of rotation, considerably exceeds thewidth of the hubs 32, so that the blades on adjacent hubs may overlapappreciably.

It will now be apparent that the impellers 2| can be pivotally adjustedabout the screws 46 to vary the angular positions of the blades 42relative to the axis of rotation. This has very great practicaladvantages, as it makes it possible to adapt the stoker to furnaces ofvarious dimensions and obtain proper distribution of the fuel. Byincreasing the angularity of a blade with respect to the axis, the bladecan be made to throw the fuel more to one side, and the lateral spreadof the fuel can be controlled in a desired manner. In general I havediscovered that th blades at the right hand side of the rotor centershould be set to deflect fuel to the right, and the blades at the lefthand side of the rotor center should be adjusted to deflect fuel to theleft. Furthermore, the blades near the center of the rotor should havethe greatest angle, the angularity of succesive blades preferablydecreasing gradually toward the ends, the end blades having little or noangularity. Thus, with nine pairs of blades as shown in Figs. 2 and 3,the pair at the center may be set at say 30 degrees, with one turned tothe right and the other to the left. The blades next adjacent may be setat say 20 degrees, the next adjacent blades at say 10 degrees, and theremaining blades (two pairs at each end of the rotor) at zero degrees,i. e. parallel with the axis of rotation. These angles may be increasedif the furnace is wide enough to require a greater lateral spread of thefuel. The construction makes it possible to obtain a very uniform fueldistribution while avoiding appreciable impact of fuel particles againstthe sides of the wall opening H.

Rierring now particularly to Figs. 1 and 4, it will be noted that thefuel-engaging faces of the impeller blades 42 are not radial but areoffset in the direction of rotation. Thus when a blade is in itsuppermost or fuel-striking position, its advancing face will be locatedsomewhat rearwardly of the shaft axis. By reason of this constructionthe rotor shaft can be mounted somewhat farther from the furnace, whereit will be better protected from the heat, while the impeller bladesnevertheless distribute the fuel particles in a desire-:1 manner. Sincethe hub members 32 cover nearly the entire outer surface of the rotorshaft within the casing 16, they are of considerable value in shieldingthe shaft from the furnace heat.

In the operation of the invention, the reciprocating ram 25 will pushfuel from the hopper 23 rearwardly over the plate 24. The fuel will fallfrom the rear edge of this plate into the path of the revolving blades52, which will throw the fuel particles rearwardly through the opening Hinto the furnace. The fine particles will burn in suspension, while thecoarse particles will fall upon the furnace grate to form a bed ofburning fuel. Because of the novel angular positioning of the blades,varying from a maximum angularity at the center of the rotor to zeroangularity at the ends of the rotor, the fuel will be distributed withgreat uniformity throughout the furnace. The same rotor can be used wi hfurnaces of different widths by varying the adjustment of the blades.The blades can be adjusted without disturbing the rotor shaft and infact while the furnace is still in operation, since the removal of thetrough section will permit ready access to the rotor. To adjust eachblade the operator needs to loosen only a single screw as, and a veryfew minutes will be sufficient, with only a brief interruption in thefuel feed. The blades are mounted in diametrically opposed pairs, withadjacent pairs displaced degrees about the rotor axis and overlapping inthe axial direction. Thus there are four rows of blades, with the bladesin adjacent rows staggered. This construction provides for dynamicbalance, it avoids any gaps along the rotor, and it pirinits angularadjustment of each blade independently of adjacent blades, all in asimple, rugged and inexpensive structure.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patcnt is:

1. A fuel distributing rotor for a mechanical stoker comprising asupporting structure rotatable about a horizontal axis and havingoutwardly facing .ne surfaces parallel with axis, a series offuel-tlnowing impellers carried by said structure and each including abase and a blade joined at approximately right angles to provide adevice L-shaped in cross-section with the blade in advai e of the in thedirection of rotation, and means fastening the bases of the impellers tothe said plane surfaces for pivotal adjustment about axes extendingperpendicular to the said surfaces.

2. A fuel distributing rotor for a mechanical stoker comprising asupporting structure rotatable about a horizontal 'axis and havingoutwardly facing plane surfaces parallel with the axis, a series offuel-throwing impellers carried by said structure and each including abase and a blade joined at approximately right angles to provide adevice L-shaped in cross-section with the blade in advance of the basein the direction of rotation, and a single screw fastening the base ofeach impeller to the corresponding plane surface for pivotal adjustmentabout the axis of the screw.

3. A fuel distributing rotor for a mechanical stoker comprising ahorizontal rotatable shaft, a series of hubs on the shaft and eachshaped to provide two diametrically opposite outwardly facing planesurfaces parallel with the axis of the shaft, a pair of diametricallyopposed fuelthrowing impellers carried by each hub, each impellerincluding a base and a blade joined at approximately right angles toprovide a structure L-shaped in cross-section with the blade in advanceof the base in the direction of rotation, and means fastening the basesof the impellers to the said plane surfaces for pivotal adjustment aboutaxes extending perpendicular to the said surfaces.

4. A fuel distributing rotor for a mechanical stoker comprising ahorizontal rotatable shaft, a series of hubs on the shaft and eachshaped to provide two diametrically opposite outwardly facing planesurfaces parallel with the axis of the shaft, a pair of diametricallyopposed fuelthrowing impellers carried by each hub, each impellerincluding a base and a blade joined at approximately right angles toprovide a structure L-shaped in cross-section with the blade in advanceof the base in the direction of rotation, adjacent hubs being turned 90degrees with respect to one another so that the blades are arranged infour rows with the blades in adjacent rows staggered, the blades in eachrow being of sufficient width to overlap the blades in the adjacentrows, and means fastening the bases of the impellers to the said planesurfaces for pivotal adjustment about axes extending perpendicular tothe said surfaces.

5. A fuel distributing rotor for a mechanical stoker comprising ahorizontal rotatable shaft having a cylindrical outer surface, a seriesof hubs on the shaft and each including a pair of oppositely disposedmembers clamped against the shaft by fastening means and providing twodiametrically opposite outwardly facing plane surfaces parallel with theaxis of the shaft, a pair of diametrically opposed fuel-throwingimpellers carried by each hub, each impeller including a base and ablade joined at approximately right angles to provide a structure L-shaped in cross-section with the blade in adranged in four rows with theblades in adjacent rows staggered, the blades in each row being ofsufiicient width to overlap the blades in the adjacent rows, and meansfastening the bases of the impellers to the said plane surfaces forpivotal adjustment about axes extending perpendicular to the saidsurfaces.

6. A fuel distributing rotor for a mechanical stoker comprising asupporting structure rotatable about a horizontal axis, and alongitudinal row of fuel-throwing impellers projecting from thesupporting structure and providing fuel-striking surfaces positioned atvarying angles with respect to the axis, the impellers at the right sideof the rotor center being set to deflect fuel toward the right, and theimpellers at the left side of the rotor center being set to deflect fueltoward the left, the angularity of the impellersdecreasing progressivelyfrom a maximum adjacent the center of the rotor to a minimum adjacentthe ends of the rotor.

'7. A fuel distributing rotor for a mechanical stoker comprising asupporting structure rotatable about a horizontal axis, and longitudinalrows of fuel-throwing impellers projecting from the supporting structureand providing fuel- :triking surfaces positioned at varying angles withrespect to the axis, the impellers bein arranged in pairs ofdiametrically opposed impellers with laterally adjacent pairs turneddegrees with respect to one another to form four rows of impellers withthe impellers in adjacent rows staggered, the impellers at the rightside of the rotor center being set to deflect fuel toward the right, andthe impellers at the left side of the rotor center being set to deflectfuel toward the left, the angularity of the impellers decreasingprogressively from a maximum adjacent the center of the rotor to aminimum adjacent the ends of the rotor.

EARLE C. MILLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

